Lawyers defending Aetna Inc.’s proposed acquisition of HumanaInc. accused the U.S. Department of Justice on Tuesday of“serious delay and misconduct” as the two health insurancecompanies demand access to regulatory information to defend their$37 billion deal.

In a request for sanctions filed in Washington federal districtcourt, the companies’ lawyers alleged the government withheld about1 million documents. And they argued the government’s allegedobstruction has “gravely undermined” the ability of the insurers tomount a defense against claims from antitrust enforcers that theacquisition would drive up the price of insurance.

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“The government’s extended pattern of dilatory conduct,misrepresentations, and violations of court orders plainlysatisfies the requirements for imposition of sanctions,” Aetna’slawyers at Jones Day wrote.Lawyers from Crowell & Moring and O’Melveny & Myers, thefirms that represent Humana, were also on the filing.

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The new filings, docketed in the predawn hours Tuesday, shine alight on the extent of discord in the blockbuster antitrust case.In August, the government sparred with the two companies overscheduling, with the Justice Department arguing that the trialshould begin in early 2017 after the year-end deadline that Aetnaand Humana set to close the deal. U.S. District Judge John Bates ofthe District of Columbia set Dec. 5 as the start date and said heexpects to issue a ruling in January.

Aetna and Humana want access to documents from the Centers forMedicare and Medicaid Services, or CMS. The companies argue acentral issue in the case “is the proper definition of the productmarket that will be used to assess the government’s claims.”

Aetna and Humana asked Richard Levie, the retired judge who’soverseeing discovery, to recommend as a sanction that Bates preventthe government from calling CMS employees to testify at trial. Thetwo companies also asked Levie to suggest that Bates preclude thegovernment from introducing certain CMS documents intoevidence.

A Justice Department spokesman declined to comment. KentGardiner, a Crowell & Moring partner representing Humana,declined to comment. John Majoras, the Jones Day partner leadingthe defense for Aetna, did not respond to a request forcomment.

In the 45-page motion, Aetna and Humana lawyers accused theJustice Department of waffling on critical decisions in thediscovery process. The companies allege the Justice Departmentinitially committed to calculating its 28-day document productiondeadline beginning Aug. 11, but later reversed course and insistedon a new round of negotiations.

Levie later ordered the government to produce documents by Sept.26. But, according to Aetna and Humana, the government missed thatdeadline and withheld between 860,000 and 1.1 million documentsbased on “potential” privilege issues.

“Ultimately, this amounted to roughly half of the documents thatresponded to the search terms the government utilized,” the Aetnaand Humana lawyers wrote.